1. Field of the Invention
The present invention relates to a coating and developing system for a substrate.
2. Description of the Related Art
In a photolithography process in semiconductor device fabrication processes, for example, resist coating treatment in which a resist film is formed on a top surface of a wafer, developing treatment in which development is performed for the wafer after being exposed in a pattern, and heating treatment and cooling treatment, which are performed before the coating treatment, before and after exposure processing, and after the developing treatment, and the like are performed. The above treatments are performed in each treatment unit individually provided, and these treatment units are integrated as a coating and developing system so that the aforementioned series of treatments can be performed in succession. Exposure processing for the pattern, itself, is usually performed in the exposure processing unit provided adjacently to the coating and developing system.
The aforementioned coating and developing system is composed of a load/unload section for carrying a substrate into and out of the coating and developing system, a processing zone having a coating unit, a developing unit, heating treatment unit and the like, in Which most of the aforementioned wafer; treatments are performed, and an interface section for transferring a wafer from/to the processing zone and the exposure processing unit outside the aforementioned system.
When the treatments for a wafer are performed in the coating and developing system, air cleaned by an air cleaner or the like is supplied into the aforementioned coating and developing system as a down flow in order to prevent impurities such as very small particles from adhering to the wafer, while an atmosphere inside the coating and developing system is exhausted so that the treatments can be performed for the wafer in a clean state.
Further, after a predetermined circuit pattern is exposed on a resist film formed on the wafer, the wafer is transferred to the heat treatment unit, whereby PEB (Post Exposure Baking) that is heating after exposure is performed, thus intending to improve the formation of a pattern.
However, an art of exposure with use of a light with a shorter wavelength (for example, 157 nm) is recently being developed in order to form a finer and more precise circuit pattern. When using the light with a short wavelength, there is a fear that impurities at a molecular level such as, for example, oxygen, ozone, water-vapor, which did not become a problem so far, have an adverse effect on exposure processing and a precise circuit pattern is not formed.
Consequently, at least when a wafer is subjected to exposure processing, it is necessary to prevent impurities such as oxygen from adhering onto the wafer, but since impurities such as oxygen are contained in the air, only supplying clean air as conventionally cannot effectively prevent the impurities from adhering onto the wafer, or cannot remove the impurities, which have already adhered to the wafer.
If the aforementioned impurities adhere to the wafer while the wafer is carried from the exposure processing unit and carried into the heat treatment unit, an adverse effect is exerted on the formation of the circuit pattern. Further, when a chemically amplifying resist film is used, if much time is taken to transfer the wafer to the PEB after the exposure processing, there arises a fear that amplification reaction of acid proceeds during that time, which causes a variation in a line width of the circuit pattern. Further, since a plurality of wafers are treated in the coating and developing system, if the transferring time of each wafer to the PEB after the exposure processing differs, namely, if PED (Post Exposure Delay) differs, a variation occurs to the line width of each wafer.
Pattern deformation to an extent that is conventionally negligible has a room for improvement at the present day when a more precise circuit pattern is demanded, and the conventional configuration with clean air and the coating and developing system cannot meet the demand.
The present invention is made in view of the above points, and its object is to provide a coating and developing system in which very small impurities at a molecular level do not adhere to a substrate such as a wafer, and a more precise circuit pattern can be obtained.
In order to attain the above object a coating and developing system of the present invention has a processing zone having a coating unit for forming a coating film on a substrate, a developing unit for performing development of the substrate, a heat treatment unit for performing heat treatment of the substrate, and a first transfer device for transferring the substrate from/to the coating unit, the developing unit and the heat treatment unit, an interface section in which the substrate is transferred at least on a path between the aforementioned processing zone and an exposure processing unit outside the system for performing exposure processing for the substrate, a casing for housing the aforementioned processing zone and interface section, a gas supply device for supplying an inert gas into the aforementioned interface section, and an exhaust portion through which an atmosphere of the aforementioned interface section is discharged, and the heat treatment unit, and a second transfer device for transferring the substrate on a path between the heat treatment unit and the exposure processing unit are disposed in the aforementioned interface section.
In the present invention, the heat treatment unit disposed in the interface section is capable of performing heat treatment immediately before exposure processing, and is also capable of performing heat treatment immediately after the exposure processing.
According to the present invention, while the inert gas is supplied to the interface section from the gas supply device, the atmosphere of the interface section is discharged from the exhaust portion, thereby making it possible to remove impurities such as oxygen and water vapor from the interface section and maintain the interface section in a clean state. Consequently, while the substrate goes from heat treatment immediately before exposure processing through the exposure processing to heat treatment immediately after the exposure processing, the substrate can be transferred in a clean atmosphere of the inert gas, and impurities can be prevented from adhering thereto. After the substrate with a coating film being formed is heat-treated, it is especially in a state in which impurities easily adhere onto the substrate. If an impurity adheres to the substrate on exposure processing, the impurity absorbs energy such as a laser light used for exposure, which causes a fear that the exposure processing is not suitably performed. However, by disposing the heat treatment unit in the interface section and maintaining the path on which the substrate passes immediately before the exposure processing in the state of the clean atmosphere of the inert gas as in the present invention, the treatment and processing of the substrate can be suitably performed.
The aforementioned inert gas means an inert gas to the treatment solutions, for example, a coating solution and a developing solution, used in the coating and developing system, and the inert gas is, for example, nitrogen gas, argon, neon and the like, which does not contain oxygen, water, and organic substances.